The exposure of pregnant women to environmental toxins is of major concern because of their potential harm on the fetus. However, the detection of fetal exposure to environmental toxins still remains a major challenge. We propose that meconium analysis is a promising tool to meet this challenge. Aims: (1) To compare the prevalence and amount of fetal exposure to environmental toxins through the analysis of meconium, cord blood and neonatal hair and to determine the degree of agreement among these three methods, (2) to determine the relationship between the prevalence and amount of maternal exposure to environmental toxins during pregnancy, as determined by serial analyses of maternal hair and blood, to the prevalence and amount of fetal exposure to environmental toxins as determined by meconium, cord blood and neonatal hair analyses, and (3) to compare adverse immediate (birth weight, length, head circumference, gestational age) and long term (postnatal growth and neurobehavioral development up to 2 yrs from enrollment) outcomes that are associated with antenatal exposure to environmental toxins as determined by maternal blood, maternal hair, meconium, cord blood and neonatal hair analyses. Study design: Pregnant women (n=750) will be recruited, at midgestation, from the Outpatient Clinic of the Bulacan Provincial Hospital, Philippines and their blood and hair will be obtained at the time of recruitment and at delivery. Umbilical cord blood, meconium and neonatal hair will also be obtained. The samples will be analyzed, by atomic absorption spectrometry, for lead, mercury and cadmium and by gas chromatography/mass spectrometry for the following pesticides and their metabolites: propoxur, transfluthrin, Malathion, DDT, chlorpyrifos, bioallethrin, pretilachlor, lindane, cyfluthrin and cypermethrin. Pertinent maternal and infant data will be obtained after birth. The infants will be subsequently followed up at scheduled intervals for 2 years, to study their physical growth and neurobehavioral development using a battery of tests. Data analysis: The relationship between the presence/amount of environmental toxins in meconium, maternal blood, maternal hair, cord blood or neonatal hair to the immediate and two year outcome in the infants will be studied, while controlling for potential confounders. The presence/amount of environmental toxins in maternal blood, hair, cord blood, meconium and neonatal hair will be also evaluated to determine which substrate (s) provide(s) the best index of exposure for a given toxin. Expected benefits: Meconium analysis may provide a powerful tool to study the prevalence and degree of fetal exposure to environmental toxins and its associated adverse effects. This project can also serve as a model for the study of environmental pollutant problems during pregnancy at a local, national or global level.